This invention relates to a system and method for providing visually impaired individuals and more particularly to a system and method of emitting ultrasound pulses to detect obstacles in the path of the visually impaired.
Based on census data from the 1990 census, the mean monthly earnings for those without disabilities has been reported as $1,962. For the severe and non-severe xe2x80x9cfunctional limitation in seeingxe2x80x9d group, the mean monthly earnings was reported as $1,573. For the severe xe2x80x9cfunctional limitation in seeingxe2x80x9d group only, the mean monthly earning was $1,238. When these numbers are calculated for a mean yearly income, the no disability work force made $23,544, the severe and non-severe limitation in seeing group made $18,876, and the severe limitations only group made $14,856. The difference in mean earnings is alarming. The visually impaired were not only unable to compete for jobs, they were unable to compete for jobs with high earnings.
Any device or technique that enables the visually impaired to move more easily in their surroundings would be of benefit. The most familiar aids are, of course, the cane and the guide dog. The cane does not alert the visually impaired to obstacles they are approaching that are beyond the reach of the cane, nor to those located above ground level, like an overhanging branch, for example. A guide dog may stop the individual from proceeding, but does not provide feedback as to obstacles in the path of the individual. In any event, neither the cane nor the guide dog is as unobtrusive as may sometimes be desired. Neither the cane nor the guide dog permits the visually impaired to navigate with both hands free.
A U.S. patent to Nelkin, Pat. No. 3,337,839 describes a guidance apparatus that uses a plurality of ultrasound transducers in an array worn by a visually impaired person. The transducers are directional and are pointed into separate locations in front of the individual. Echoes of the ultrasound pulses from the transducers are identified on the basis of time of receipt and are used to stimulate an array of vibratory devices also worn by the user. The vibratory devices mimic the locations of the ultrasonic transducers to indicate where, in front of the user, an obstacle may be encountered.
Elchinger U.S. Pat. No. 4,280,204 dated Jul. 21, 1981 describes a modified mobility cane for the visually impaired. It is described as capable of chest and/or face height detection at multiple distances. The transducer is ultrasonic and is mounted on the cane. The output is auditory, sent by wire to an earphone. The design is advantageous to the extent that it allows the user to have one free hand. It also is described as having a short range and a long range option for detecting chest height obstacles or face height obstacles. The zone of detection is described as being adjustable. The design is disadvantageous because the output is through an earphone, which could be uncomfortable and impede the visually impaired user""s ability to hear. The user does not have both hands free. The single transducer does not appear to provide sufficient information as to location of an obstacle being approached.
U.S. Pat. No. 4,459,689 of Biber dated Jul. 10, 1984 is for a multiple zone object detection system. This system uses ultrasonic sensors to detect multiple environmental zones. Like the Nelkin patent, Biber distinguishes between each zone on the basis of the time of receipt of echoes of the serially transmitted ultrasound signals. The Biber patent does not refer to guidance for the visually impaired.
Two U.S. Pat. Nos. 4,658,385 and 4,636,996, both to Tsuji, describe an ultrasonic obstacle detection system and methodology using a CPU for mobile robot control. The system uses three transmitters, two receivers, a CPU and data ROMs. It calculates the location of an obstacle with spatial coordinates and the time difference between wave transmission and reception. The timing of echoes received at the two receivers is used to specify location coordinates of obstacles.
Vanmoor U.S. Pat. No. 5,982,286, issued Nov. 9, 1999, is for another electronic travel aid for the visually impaired. The frame of a pair of eyeglasses houses the sensors, circuitry and power source. The output is auditory. A benefit is that the system must always be worn in the same way, insuring proper sensor placement. As the wearer moves closer to an obstacle a beeping output becomes louder and more frequent. The patent does not describe any output indication of location other than distance from the wearer. The audible outputs are by the individual""s ears, which can interfere with the user""s hearing.
In 1970, Geoff Mowatt, created a sensor that, when it detected an obstacle, a vibratory output would stimulate its user""s hand. As the distance to an obstacle decreased, the frequency of vibration increased. This device had an adjustable detection range for short distance (3xe2x80x2) and long distance (12xe2x80x2). The Mowatt sensor is believed to have been commercially the most successful electronic travel aid (ETA) thus far. It had roughly 30 years of commercial availability.
In 1971, the United States Veterans Administration evaluated the C-4 Laser Cane to be used by blind veterans. One of the veterans in the evaluation program wrote, xe2x80x9cit was designed to detect obstacles hanging overhead or protruding from the sides at head level within the path of travel; to detect objects in front and between the left and right arc; and to detect such downdrops as deep curbs, stairways, and from platforms.xe2x80x9d The advantage of the Laser Cane is that is was a primary aid that could detect all obstacles in front of its user. This was also one of the major disadvantages. A complex electronic device, such as the Laser Cane, consumes power and runs out of power. The user may end up stranded. Another disadvantage is the extensive amount of training required to be proficient with the Laser Cane. The veteran who used the device went through five weeks of intense training. Few people with full time employment can afford to take such time away from their jobs. A further disadvantage is cost. Complex devices like the Laser Cane are expensive to manufacture and are built with expensive state-of-the-art sensing equipment. Few visually impaired people are in the position to take the time and spend the money to use the Laser Cane.
The newest generation of electronic travel aids (ETAs) is far more sophisticated than previous generations, thanks to the microprocessor. A research team at the University of Michigan developed an ETA called the xe2x80x9cGuideCane.xe2x80x9d It is an enhanced seeing-eye cane that uses an array of ultrasonic sensors to detect obstacles in its user""s path. The sensors and processor circuitry are at the front end of the cane, attached to two large wheels. The user chooses the direction of travel by using ajoystick attached to the cane""s handle. This propels the cane and user in the desired direction. When an obstacle is detected, the GuideCane measures the distance and orientation to the obstacle and steers the user around. Unfortunately, the design of the GuideCane system warrants some questions about user safety. It is not clear how well the GuideCane handles floor obstacles, such as curbs and steps. There is a strong possibility of injury to the user or other people when navigating through crowded places. The system guides the user past detected obstacles, but if someone or something moves between the user and the sensory equipment (i.e., a closing door or a hurried pedestrian), the user or intervening person could sustain injuries. It is not clear whether or how chest and face height obstacles are detected. Once again cost is believed to be a drawback.
Another new ETA, the Navbelt, uses a belt of ultrasonic sensors to create a complete environmental map of its wearer""s surrounding environment. The technology is based on real-time signal processing optimized to solve for obstacle avoidance. Eventually, it could be combined with global positioning to give its wearer the capability of navigation through unknown environments. Cost is again a concern.
There remains a need for a navigational aid for the visually impaired that quickly and accurately identifies the location of obstacles in the path of the user, that gives its user a useful range of detection that is easy to understand and so requires very little training, that does not interfere with the use of the user""s hands, and that is relatively inexpensive to manufacture, durable, small and light, and has long battery life.
In accordance with a preferred embodiment of the present invention, a system and method of assisting a vision impaired person to recognize obstacles includes the direction of a first ultrasound pulse in a first direction from the person, detection of an echo of the first ultrasound pulse to the person when an obstacle is located in that first direction and direction of at least a second ultrasound pulse in a second direction away from the person and detection of an echo of the second ultrasound pulse when an obstacle is located in the second direction. The system then generates, in dependence upon whether an echo of the first tone or the second tone is received, either a first tone of a first discernable, non-visible characteristic (such as specific frequency) or a second tone of at least a second discemable, non-visible characteristic (such as a second, different frequency). Preferably the tones thus generated are audible tones at the first and second frequencies. Preferably, too, the first and second ultrasound pulses are just two of a series of four or more pulses from an array of ultrasound transmitters. Each pulse, if echoed to a receiver or receivers, causes the generation of a distinctive audible tone.
In one preferred embodiment the ultrasound pulses are themselves distinguishable. The first has a first detectable characteristic, the second has a second detectable characteristic and so on, such that echoes of the tones can be recognized based on those detectable characteristics of the first and second pulses.
In another preferred embodiment the time of receipt of an ultrasound pulse is the basis on which it is determined that it is the echo of a particular ultrasound pulse. The generation of audible tones"" first and second frequencies can be accomplished by providing a plurality of signal generators coupled to a speaker, each of the signal generators having one of the first and second frequencies and being activated upon receipt of the first or the second ultrasound pulses. Alternatively, a variable frequency signal generator may be controlled on the basis of which ultrasound pulse is identified as having been echoes to the vision impaired user.
In the case where the ultrasound pulses have first and second detectable characteristics, these may be ultrasound pulses of first and second (or more) frequencies. These first and second frequencies need not be the ultrasonic frequencies, but a lower frequency pulsation or modulation of the pulse of ultrasound. A series of ultrasound transducers may be serially and repeatedly excited to produce ultrasound pulses spaced apart temporally and emanating in different directions from the person so that the time of receipt of any echo will be indicative of the location of an obstacle in the path of the individual. The sampling frequency is important for detecting head and chest height obstacles and for detection at a useful range, while also making the system easier to understand. Also, when the sampling rate increases, more power is consumed. This means that the sampling frequency is also related to long battery life.
Preferably the audible signals or tones increase in rapidity of repetition as the distance to the obstacle decreases. That distance can be determined from the elapsed time from the emission of the ultrasound pulse to the receipt of its echo.
In one embodiment a plurality of ultrasound transmitters are located on the person of the sight-impaired individual. Each differs at least slightly in direction of emission. Each transmitter is paired with a receiver located to receive echoes from objects located in the direction of its associated transmitters"" emission. In that case, each ultrasound receiver activates production of a recognizable output. Based on a discernable characteristic of that output the user can recognize the direction from which an echo is received from an obstacle. Again, a series of oscillators operating at different frequencies may be the source of the differentiating characteristics of the audible tones that identify the direction in which an obstacle lies or a variable oscillator may be employed.
The system of one embodiment includes a timer or clock that controls the timing of a source of exciting electrical signal driving the ultrasound transmitters. The timer or clock is also operatively coupled to time the receipt of an echo at the ultrasound receiver and tone generator so that emission of an ultrasound pulse can be precisely timed and its receipt detected within a time period to determine which pulse transmitter has been echoed and consequently the direction from which an echo has been received.
In a specific preferred embodiment four piezoelectric ultrasound transmitters are employed. At least one piezoelectric ultrasound receiver receives echoes from the four transmitters. An excitation electrical signal generator has its output divided among the transmitters by an analog multiplexer such that the transmitters are pulsed one after another at 29 Hz. At least one tone generator operates to produce tones at 10 kHz, 5 kHz, 2500 Hz and 1250 Hz for application to a speaker. The first of the ultrasound transmitters is aimed to transmit ultrasound pulses at objects generally corresponding to the height of and in front of the user""s head. The second of the transmitters is aimed to transmit ultrasound pulses at objects generally corresponding in height and in front of a left location on the user""s torso. The third transmitter is aimed to transmit ultrasound pulses at objects generally corresponding in height and in front of a right location on the user""s torso. And the fourth of the transmitters is aimed to transmit ultrasound pulses at objects generally corresponding in height and in front of a centered location on the user""s torso. The at least one speaker-exciting tone generator produces the 10 kHz, 5 kHz, 2500 Hz or 1250 Hz tones depending upon which of the four transmitters produces a detected echo.